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Your Ultimate Guide to VoIP Security: Risks To Watch for, Best Practices, and More

This article was updated on July 1, 2024

Businesses are increasingly turning to Voice over Internet Protocol (VoIP) for their communication needs, as it offers a cost-effective and flexible alternative to traditional phone systems.


But as with any internet-based technology, VoIP systems can be vulnerable to security attacks. This guide will explore the different types of security risks they face, how to secure your VoIP environment, and best practices to consider.

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Are VoIP Phones Secure?

When it comes to the security of VoIP phones, the answer is not a simple yes or no. While they can be highly secure — provided you choose a reputable online phone service provider and follow best practices (more on this later) — there are still risks that must be considered.

A well-implemented system can offer robust security features, such as encryption, secure protocols, and multi-factor authentication. Having said that, no technology is 100% secure, and VoIP solutions can be a tempting target for malicious hackers. It’s important to be aware of the kind of threats you might face in order to counteract them.

Understanding VoIP Vulnerabilities and Threats

If you want to avoid falling victim to VoIP-related security breaches and enable secure communications and collaboration within your organization, you need to keep up-to-date on the latest security threats.

Let's explore some of the most common types of risks associated with VoIP.

Denial of Service (DoS) Attacks

These attacks aim to overwhelm VoIP servers or networks with a flood of traffic, rendering them unavailable to legitimate users. They can disrupt communications, causing downtime and productivity losses.

Hackers can exploit unprotected VoIP servers and force shutdowns of other systems due to taking up your network’s entire available bandwidth. In order to avoid this,  it's essential to have robust network security measures in place.


Attackers will often use emails with virus-infected file attachments or phony sites to launch malware attacks such as viruses, trojans, and worms. These can spread across your network, infecting multiple devices and systems.

In particular, malware can compromise the security of VoIP communications by allowing attackers to eavesdrop on calls, steal sensitive information, or gain unauthorized access to the system.

Regular software updates, endpoint protection, and employee education on safe computing practices can help reduce the risk of malware infections.

VoIP Phishing (Vishing)

Vishing, or voice phishing, is a social engineering technique where attackers use VoIP systems to trick individuals into revealing sensitive information, such as login credentials or financial details.

Attackers may spoof caller IDs or use persuasive tactics to manipulate employees into giving them access to the system. Educating employees about vishing techniques can help prevent successful attempts.

Eavesdropping or Call Interception

Your calls can be vulnerable to eavesdropping or interception if proper security measures are not in place. Attackers may attempt to intercept VoIP traffic to listen in on confidential conversations or steal sensitive information. Encrypting VoIP calls using secure protocols like TLS or SRTP can help protect against this and ensure the privacy of your communications.

Toll Fraud

This occurs when attackers gain unauthorized access to a VoIP system and make costly international or premium-rate calls, resulting in significant financial losses for the victim. Attackers benefit by taking a share of the proceeds from these calls, usually sold via low-cost call tariffs or overseas calling cards.

Implementing strong authentication measures, monitoring call logs, and setting up alerts for unusual calling patterns can help detect and prevent toll fraud.

War Dialing

War dialing involves using automated tools to dial a range of phone numbers to identify vulnerable VoIP systems or extensions. The tool will dial each number and analyze the responses it receives to spot vulnerable systems. Attackers then exploit poorly secured systems to gain unauthorized access.

Regularly auditing your VoIP system for vulnerabilities and implementing strong access controls can help mitigate the risk of war dialing. You can also set up an auto-attendant to disconnect calls after a specified number of failed attempts to enter the correct password or extension.

Spam over Internet Telephony (SPIT)

SPIT refers to unsolicited bulk calls or voicemails sent over VoIP networks, similar to email spam. These calls can be disruptive, consume bandwidth, and potentially lead to more severe security threats. Implementing call filtering, blocking known SPIT sources, and educating users on how to identify and report SPIT can help minimize its impact.

Voice over Misconfigured Internet Telephones (VoMIT)

VoMIT attacks exploit misconfigured VoIP devices or systems to gain unauthorized access, eavesdrop on calls, or launch other attacks. These vulnerabilities often come from default or weak device configurations.

Properly configuring VoIP devices, regularly updating firmware, and following best practices for secure unified communications can help prevent VoMIT attacks.

How To Choose a More Secure VoIP Service

Choosing a reliable and trustworthy VoIP provider is the best first step in ensuring the security of your business communications.  Here are some important factors to bear in mind:

Security and Compliance Accreditation

Look for VoIP providers that have earned industry-recognized security and compliance accreditations. For example, Vonage invests heavily in security and privacy measures and maintains a wide range of compliance certifications across our product lines. They include ISO 27001, PCI-DSS, SOC, HITRUST, and CSA STAR, to name just a few.

These certifications mean that the provider has implemented stringent security controls and adheres to industry-leading best practices for the protection of customer data.

  • ISO 27001: This international standard indicates that the provider has implemented an information security management system to ensure that customer data is protected. ISO 27001 certification ensures that the provider follows best practices for risk management, access control, and continuous improvement.

  • The Cloud Security Alliance (CSA) Security, Trust, and Assurance Registry (STAR): This assesses the security standards of cloud service providers, including VoIP providers. Certified providers must meet strict requirements and observe best practices for safeguarding cloud services.

  • HIPAA compliance: If your business is in the healthcare sector, choose a provider with security measures that can protect patient information transmitted over your network.

  • PCI-DSS: If you take payments over the phone, you should look for a provider that complies with the Payment Card Industry Data Security Standard (PCI-DSS). This guarantees there are methods in place to protect cardholder data and reduce fraud risks.

Providers with these accreditations undergo regular audits to ensure they maintain high security standards, so you can be confident your communications are protected.

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Without encryption, secure VoIP communications aren’t possible. Make sure the provider offers strong encryption for your calls as well as for data transmission.

Look for providers that use protocols like:

  • Transport Layer Security (TLS): This Is an industry-standard encryption protocol used to protect signaling messages between VoIP devices and servers to keep call setup information and other metadata encrypted and out of the hands of eavesdroppers.

  • Secure Real-Time Transport Protocol (SRTP): This protocol encrypts the actual voice and video data transmitted during a VoIP call. It stops eavesdroppers from listening in on your conversations and will make sure your calls are confidential. Look for providers that use SRTP with strong encryption algorithms, such as AES-256.

  • End-to-end encryption (E2EE): Some providers provide end-to-end encryption, meaning that voice and video data is encrypted on the device of the person sending the data, so only the person intended to receive the data can decrypt it.

Help and Support in the Event of Issues

No matter how strong the security measures you have, issues can still arise. So when choosing a VoIP provider, consider how well they can support you in the event of a security incident.

  • 24/7 technical support: Make sure that your provider offers round-the-clock technical support. Security breaches and emergencies don't wait for the regular 9 to 5, and neither should tech support.

  • Dedicated security team: The provider should have a dedicated security team with expertise in VoIP security. The team should be responsible for monitoring the provider’s network, investigating security incidents, and taking the steps necessary to prevent such issues in the future.

  • Clear escalation paths: Make sure the service provider has a clear path for escalating and addressing security concerns. This includes a dedicated point of contact for security issues, a formal process for escalation, and a way of tracking incident resolution progress.

Other VoIP Security Best Practices

Choosing the right provider is just the beginning. There are several other best practices that can help you secure your VoIP systems, prevent unauthorized access, and detect intrusion attempts and other suspicious activity.

Use Strong Passwords and Multi-Factor Authentication (MFA)

Ensure that all user accounts have strong, unique passwords — including uppercase and lowercase letters, numbers, and special characters — and require periodic password refreshes.

For added peace of mind, take advantage of multi-factor authentication. MFA requires users to submit two forms of identification — a password and a one-time code sent to their phone, for example — so even if hackers steal the password, unauthorized access still isn’t possible.

Keep All Software and Systems Up-to-Date

Update your VoIP software, firmware and associated systems regularly to ensure you have the latest security patches and bug fixes.

If possible, set up auto updates; schedule and keep a calendar for manual checks and updates, and make use of a mobile device management (MDM) solution to centrally manage employee’s devices.

Monitor Call Logs and Analytics for Suspicious Activity

Make a regular habit of checking your VoIP system’s call logs and reporting metrics to uncover rogue activity or any other oddities.

Look for unusual calling patterns, such as an unusually high number of calls to international or premium-rate numbers, calls outside of business hours, or calls from non-standard IP addresses.

Detecting these anomalies in a timely manner can help you detect and prevent toll fraud, unauthorized access attempts, and other security breaches. You can set up alerts or notifications for these types of anomalies to ensure you’re notified as soon as they occur.

Implement Sensible Security Policies

Create and enforce sensible security policies to reduce the likelihood of VoIP-related security incidents. These policies might include:

  • Regularly deactivating unused accounts: Decommission user accounts as soon as employees leave the company or no longer need VoIP access. Unused accounts are targets for unauthorized access by attackers.

  • Limiting access to certain features: Use role-based access control to limit employees’ access only to the features and functions of the VoIP service that they need to perform their job. This principle of least privilege reduces the “blast radius” of a compromised account.

  • BYOD policies: If your organization supports employee-owned devices for work purposes, develop a detailed Bring Your Own Device (BYOD) policy, including rules for securing VoIP applications and data on employees’ devices. This might include requirements for device encryption, password protection, and regular software updates.

Educate and Train Your Staff in Security

Empower your employees to fight against VoIP security threats by providing regular security education and training. Have clear processes in place to report suspicious activity, and make sure they can recognize social engineering mechanisms, such as vishing.

Remind staff to be wary of giving out confidential information over the phone, and to check identifications before disclosing any confidential information.

Invest in Technological Solutions

There are many smart solutions that can help improve the security of your systems, including:

  • VoIP-Specific Firewalls: By having a VoIP-specific firewall like a Session Border Controller (SBC) in place, you can provide an additional layer of security between your VoIP network and the internet.

  • Virtual Private Networks (VPNs) for Remote Workers: If employees are working remotely or using VoIP services on public networks, ensure the connections are secured by using VPNS to encrypt the data transmitted between the remote device and your VoIP network.

  • Voice VLAN Segmentation: This separates your VoIP network from threats on your data network. That way, attacks like DoS can’t bring down your entire business.

Conduct Regular VoIP Security Audits and Penetration Testing

Conduct regular security audits to find any outdated components, misconfigurations, and vulnerabilities that an attacker could exploit. You can also use penetration testing to act out what attackers would do if they were trying to get around your security. This should help you find the weak spots in your VoIP security and fix them before they can be used against you.

Regularly Backup and Test Restore Procedures

Back up your VoIP system configuration, user data, and call logs so that you can quickly recover from a security incident or system failure. You should also test your restore procedures to ensure that your backups are working properly and that your system can be restored in an emergency.

The Journey to Secure VoIP Begins With Choosing a Trustworthy Provider

Securing your VoIP system is a vital part of safeguarding your business communications and data. While the many benefits of the technology — including cost savings, flexibility, and improved collaboration — are well documented, security remains paramount to protecting against threats and vulnerabilities.

With an established and reputable VoIP provider on one side, and a positive security culture in the workplace on the other, you will be best prepared to minimize the chances of a security breach.

Of course, no system is ever entirely secure, but if your security strategy is multi-layered and comprehensive, you’ll be in the best possible position to secure your business communications, safeguard your trusted relationships with both customers and stakeholders, and protect your reputation.

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